As the demand for smaller electronic devices continues, the dimensions of components used in such devices must decrease. Integrated circuit packages found in electronic devices are no exception. One common way that manufacturers have decreased the size of integrated circuit packages is through the use of solder balls. In a flip chip design, for example, solder bumps on a die are used eliminate wire bonds from the die to a substrate of the integrated circuit package. That is, a solder ball, often called a solder bump when formed on a contact pad of the die, enables a connection between the contact pad of the die and a corresponding contact pad of the substrate, as is well known in the art. Similarly, solder balls of a Ball Grid Array (BGA) device eliminate the need for leads normally used to connect the integrated circuit package to another device, such as a printed circuit board. In either case, the array of solder bumps on a die of a flip chip device or solder balls on a BGA package increases the input/output (I/O) density of the device by enabling the positioning of I/O pads anywhere on the die or integrated circuit package. In addition to reducing size of the integrated circuit package, the elimination of wire bonds and leads from a conventional package also lowers inductance and resistance, and provides better noise performance.
However, as with any bonding technique, it is important to ensure that the solder bumps or solder balls provide a reliable connection. In manufacturing semiconductor components, it is important that the components are free of defects and remain reliable throughout their use. When defects are present in an integrated circuit package, the percentage of usable devices decreases, and the profitability of the manufacturer will be impacted. Further, when an electronic device has an integrated circuit package which has a defective connection of a solder ball, the integrated circuit may function improperly or fail, and may cause an electronic device having the integrated circuit to function improperly or even stop functioning. Accordingly, it is important that defects in integrated circuit packages are minimized whenever possible.
One common source of failures in integrated circuit packages is found where components are soldered to contact pads. Many components are soldered to contact pads using solder balls which are reflowed when the component is placed. For example, a flip chip is soldered to a substrate by reflowing a plurality of solder bumps on the flip chip, and a ball grid array (BGA) is soldered to a printed circuit board by reflowing a plurality of solder balls on the BGA, as is well known in the art. Failures in the solder connection may be caused by a variety of defects in materials, such as poor solder quality, inadequate solder amount or other factors. On common cause of failures when soldering a flip chip to a substrate in a BGA device, or soldering a BGA device to a printed circuit board, is a solder crack at a junction with the contact pad. The crack normally initiates and propagates at the interface between contact pad and the solder ball. A BGA package reduces real estate requirements of a printed circuit board, provides more circuitry per unit area and facilitates automation of substrate assemblies. Hence, the demand of BGA packages has increased dramatically over last several years. However, the thermo-mechanical reliability of these packages is a concern for the electronics industry. The board level reliability of a solder joint is one of the most critical issues for the successful application of a BGA. While it is well know that increasing a solder ball pad opening size may improve the solder joint reliability, the pad opening size must be within a certain size which may not be increased for high density package design.
Accordingly, there is a need for an improved contact pad and method of forming a contact pad for an integrated circuit.